I can confirm the carrier interface charge doesn't apply at the airport.
My one-way flight was $93.80 online, $47.80 at the airport. The difference is the $46 Carrier Interface Charge ($23/leg * 2 legs because I had a stop).

I was worried it wouldn't work because there was a sale with a promo code, but I did end up getting the same fare at the airport (but without the CIC added on). Though I'm not sure the ticket I bought was covered by the sale.

Online ($93.80):

1. $17.67 airfare
2. $1.33 US transportation tax
3. $46 carrier interface charge
4. $11.20 US passenger security fee
5. $8.60 US domestic flight segment tax
6. $4.50 * 2 passenger facility charge (one for each departure airport)

Airport (Total: $47.80):

1. $19 airfare (looks like this combines the $17.67 airfare and $1.33 US transportation tax)
2. $28.80 fees & taxes

As a bonus, if you're nice to the ticket agent they might assign you seats, too. I was assigned a window seat near the front of the plane for both flights, which would've cost $26 * 2 if I paid for them.